Straining equipment



Dec. 19, 1939. D. R. MCNEAL STRAINING EQUIPMENT Filed Oct. 27, 1938 2 Sheets-Sheet l INVENTOR g @M 4f 'I, ATTORNEYS Dec. 19, 1939. D. R. MCNEAL STRAINING EQUIPMENT Filed oct. 27, 193s 2 Sheets-Sheet 2 wy J A'I'TORNEYS las rsi

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Patented Dec. 19, 1939 UNITED STATES PATENT OFFICE STRAINING EQUIPMENT Application October 27, 1938, Serial No. 237,163

6 Claims.

The present invention relates to strainers of the type wherein the straining element is movable and wherein means are provided for progressively cleaning it by reversal of fluid flow through successively segregated sections or areas of the straining element, but without interruption of service through other portions oi the ,straining element. Such equipment may take various forms, but the best exempliflcation there of is probably the so-called rotary type of strain'- er shown, for example, in my previous Patents Nos. 1,826,361 and 2,057,497, as well as in my copending application Serial No. 77,110, led April 30, 1936. In fact, the present invention is in the nature of an improvement on the control mechanism illustrated in the above-mentioned pending application. In View of this, it will be shown and described as embodied in a rotary strainer of the kind disclosed in said patents and application.

The primary object of the invention is to improve the certainty and uniformity of opera-tion of straining equipment of this general character. Associated with this object is the provision of means for ensuring at all times the maximum capacity from the strainer regardless of the condition of the fluid being strained.

It is also an object of the invention to obtain the foregoing by means of an improved control mechanism for the straining equipment which is entirely automatic in its operation and which will respond not only to a drop in pressure across the straining element, but also to a periodically operated time switch which is set in such relation to the character of the iiuid being strained as to prevent the .deposition or growth of hard or difcultly removable deposits on the cleaning surface of the straining element. Deposits of this kind are encountered most frequently in instances where the liquid being strained is relatively free of contaminations or dirt so that the pressure control is called upon to function at very infrequent intervals. Where this occurs the deposit sometimes becomes what is termed calcined so that when the cleaning fluid is finally supplied and a cleaning operation attempted, only a small fraction of the deposited material will be removed.

Another object of the invention is to render straining equipment of this kind substantially fool-proof in its operation, so that, regardless of any errors either of omission or commission on the part of the operator in charge, the equipment will continue to function with its maximum eiiiciency.

Other objects and advantages will appear as the description proceeds and will be better understood by reference to the accompanying drawings, wherein- Figure l is a side elevation of a rotary strainer of the type for which my invention is particularly suitable, with the upper portion of the strainer shown in vertical section;

Figure 2 is an end view taken from the left of Figure l with the upper half of the strainer casing removed in order to more accurately disclose the construction; and

Figure 3 is a diagram illustrating the principal features of my invention as applied to a strainer of the type shown in Figures 1 and 2.

Referring to the drawings, and, in the first instance, to Figures l and 2, it will be seen that I have illustrated a rotary strainer comprising, in general, a bottom casing 4, a top casing 5, a straining wheel '6, and a pair of oppositely disposed olean-out boxes 7 and 3. The straining wheel 6 is mounted for rotation upon the shaft 9 lying in the plane which divides the lower casing member 4 from the upper casing member 5.

The lower casing member is provided with. an inlet section l and a corresponding outlet section H, both of which are suitably flanged as at l2 to receive the complementary flanges i3 on t'he pipe connecting sections i4 and i5. The fluid to be cleaned enters from the left and is discharged from the right, shown by the arrows in Figures 1 and 3, the straining taining place, of course, as the fluid passes through that portion of the straining wheel which is in line with the iluid iiow in the annular chamber formed by the lower and upper casing members 4 and 5.

The shaft 9 is journaled in suitable bearings I6, and may be driven in any desired manner as by the shaft l'l, the vdetails of which driving mechanism are not illustrated inasmuch as they form no part of the present invention.

r1`he straining wheel El, as is more fully illustrat'ed and described in my Patent No. 2,057,497 above referred to, is provided with a series of spokes i3 between which are fitted the straining elements i9 of any suitable or desired character. In Figure l, the straining elements I5 are shown as being located to the right" of the center of the straining wheel 6 in order to provide a series of straining pockets 23 between the spokes i8, in which pockets the debris may collect.

The wheel rotates in the direction of the ar row shown in Figure 2 and, as the straining elements I9 in the pockets 20 are successively brought between the oppositely disposed cleanout boxes 'l and 8, luid may be supplied in the reverse direction to wash or clean the straining elements, the cleaning fluid coming in through the pipe 2| which is connected to the wash water inlet portion 22 of the lower casing member 4. In turn, the portion 22, of course, through suitable passages in the casing is connected with the box 8. Similarly, on the outlet side the box 7 -is connected tothe outlet portion 23 which, in turn, discharges into the wash water discharge line 2li.

The faces of the wheel 6 where they come opposite the clean-out boxes l and 8 are tightly sealed by means of suitable resilient or rubber gasket means 25, the nature and function of which are more fully illustrated and described in my Patent No, 2,057,497 above referred to. Sufce it to say for the present application that these sealing devices 25 effectively prevent leakage of fluid in either direction between the straining circulation and the wash circulation. Incidentally, the wheel d is sealed at its periphery by means of a suitable sealing device 26 so that fluid may not pass from one side to the other except through the strainer.y In other words, the uid which is being strained enters at lil, passes through the straining wheel 6 over that area which is not opposite the cleaning boxes 'l and 8, and then leaves through the connection I5, and the wash iluid enters at 2l, passes through the connection 22 and the clean-out box B, from whence it traverses the straining element which is in position between the two boxes and 3, in a direction opposite to that which takes place during thescreening operation, and then outward through the box l, the connection 22 and the pipe 23.

The equipment so far described is now iamiliar to those skilled in the art .and is known fundamentally as a rotary strainer. The specific improvements which form the invention of the present application will now be described, reference being had primarily to Figure 3.

It will be assumed that water is to be strained and that delivery to the strainer is made through the line 2l. In this line is a main water control valve 23, The cleaned water is discharged through the line 29 in which is another control valve 3G. Wash water for cleaning the strainer is taken from the line 2s through the line 3l which has a branch 32 leading to a booster pump 33, and another branch 3d leading to an automatically actuated control valve The pump 33 can discharge into the line 3d through the pipe 36, the point of entry into the pipe 3d being in advance oi the valve 35. A check valve 3l is placed in the line 3s in advance oi the point where the line 36 comes in so as to prevent back-ow- The pipe 3d discharges through the pipe 38 into the inlet pipe 2l on the strainer. If required, a pipe 39 bypasses the valve 35. In the pipes 32, 34, 36 and 39 are suitable hand-actuated control valves lil which are placed in these lines simply for purposes of convenience or in case some part of the automatic system should fail to function properly.

The flow of the cleaning fluid is controlled in the following way. The diierence in pressure between the two sides of the straining Wheel is delivered to a dii'erential pressure switch il! through the pipes d2 and 43, the pipe i2 being connected to the inlet side of the strainer and the pipe 43 to the outlet side. The switch il is set to operate at any desired diierence in pressure between the two sides and when this diierence exceeds the predetermined standard, the control mechanism will function to deliver cleaning fluid to the clean-out boxes 'l and 8 and so clean the strainer. In the lines l2 and i3 are located suitable pressure snubbers lill.

In the control box i5 associated with the differential pressure switch 4l is located any suitable mechanism familiar to the art whereby current coming in from the circuit @il may be passed to the control box fil' of the valve 35 and to the magnetic switch 48 which controls the circuit for operating the motor is of the booster pump 33. In other words, when the pressure differential exceeds the predetermined amount, the switch dl will be operated to deliver current to the control box dl and the magnetic switch 48 in order to open the valve 35 and simultaneously to run the booster pump motor 49 in order to deliver cleaning uid to the clean-out box 8.

As the cleaning operation progresses, the drop in pressure between the two sides of the strainer will become less andless until the predetermined standar-d is again attained, at which time the switch lli will operate the controls in the box [i5 to shut on the current and close the valve 35 and stop the booster pump motor 49 so that no more cleaning luid will be delivered to the cleanout boxes.

In addition to the control already described, the box i5 also contains a timer 4relay or switch which can be set to periodically complete the circuit of the valve 35 and the pump 33 at any interval desired. This will depend very largely, of course, upon the type oi cleaning which is being done, the character oi the water, the nature of the debris, and so forth. However, this mechanism is peculiarly adapted for use where the water being strained is unusually clean and the debris collects relatively slowly in the pockets 2li, especially where such debris is -o a rather fine nature. This may occasionally result in a build-up of the debris or a calcining, as it is called, resulting in a very difrlcultly dislodged material, so diicult in fact that when the wash water is turned on it is many times impossible to dislodge more than l to 20%. With this in mind, the timing switch is set to function at intervals which are sufficiently frequent to prevent such build-up or calcining or" the material. this way I am enabled to insure complete uniiormity and certainty of operation under all possible conditions of service.

In the diagram of Figure 3, the pipes 2l, 42 and i3 are provided with pressure gauges 50 so that the pressures may be conveniently read, if necessary. These, however, form no part oi the present invention. Valves l are simply gauge valves and the valve 52 is a plug cock. There is also a pressure snubber M in the line which connects the pipe 2i with its gauge 50.

The external circuit for operating the booster motor pump lli) is shown at 53, and this same circuit also operates the strainer driving mechanism indicated diagrammatically as a whole at 5t, the shaft 55 being connected to the shaft Il, shown in Figure l.

It will be seen that the system is entirely automatic, and that the strainer will be cleaned whenever the predetermined difference in pressure bei tween the two sides of the strainer is exceeded or whenever the timing switch functions. The timing switch functions in a way which may be described as a conditioner for the rest of the system. In other words, the periodic operation 7d of the system by means of the timing switch maintains .it in proper condition to function correctly at times when the demand is suddenly increased and full iiow of cleaned water must be delivered through the strainer. Naturally, at such times the debris accumulates rapidly and the control exercised by the difference in pressure across the two sides of the strainer will come into operation at frequent intervals, and it is important that when the difference in pressure calls for a cleaning operation that such cleaning operation be promptly, eiectively and thoroughly accomplished, so as not to interfere with the service to which the water is being put.

Although it is not absolutely necessary to take the cleaning water from the line 2?, yet there are many instances where this is the only source of supply suitable for the purpose, and in some instances it may be preferred for one reason or another. However, where so taken, as indicated in Figure 3, it is important that the cleaning water be Adelivered. under proper pressure, which is taken care of by the pump 33, and also that when the cleam'ng operation is completed there shall be no wastage of water through the cleanout line. All wastage is prevented by the positive control exercised by the valve 35 which acts simultaneously or substantially simultaneously with the pump 33. Furthermore, it is important to stop the flow or" the cleaning fluid entirely when cleaning has been effected, because otherwise there will be a reverse operation of the pump 33, especially ir the cleaning water is delivered thereto under considerable pressure.

The various control devices associated with the electrical mechanism such, for example, as the relay 48, the control box 47, the diierential pressure switch 4|, and the several switching mechanisms in the box 45, are all of a standard construction, and may take any one of various forms. The details of these mechanisms form no part of my invention, and they are, therefore, not illustrated.

I claim:

1. In rotary straining equipment wherein the straining element is cleaned by reversal of uid flow without interruption of service, the combination of a line for supplying cleaning iuid, a line for discharging the material removed by the straining element, motor actuated means in the cleaning iiuid supply line for controlling the flow which passes therethrough, a pilot mechanism for controlling the motor of said control means, said pilot mechanism being subject to the diierence in pressure between the two sides of the straining element whereby said control means may be opened when the diierence in pressure exceeds a predetermined standard and closed when the difference in pressure falls below said standard, and timing mechanism for periodically actuating said motor actuated controlling means regardless of pressure conditions in the strainer.

2. In rotary straining equipment wherein the straining element is cleaned by reversal of iuid iiov: without interruption of service, the combination of a line for supplying cleaning iiuid, a line for discharging the material removed by the straining element, a booster pump in the cleaning fluid supply line, a valve in the cleaning fluid supply line, motor means for actuating said pump and said valve, a pilot mechanism subject to the difference pressure between the two sides of the straining element, said pilot mechanism being adapted to initiate operation of said motor means so as to cause said pump to deliver cleaning fluid through said supply line and simultaneously to open the valve in said supply line when the diierence in pressure exceeds a predetermined standard and to stop said motor means so as to discontinue operation of said pump and close said valve when said standard is again attained, and timing mechanism for periodically opening said valve and operating said pump regardless of pressure conditions in the strainer.

3. In rotary straining equipment wherein the straining element is cleaned by reversal of fluid flow without interruption of service, the combination of a line 'for supplying cleaning iiuid, a line for discharging the material removed by the straining element, a booster pump in the cleaning iiuid supply line, a motor for operating said pump, a pilot mechanism subject to the diierence in pressure between the two sides of the straining element, said pilot mechanism being adapted to initiate operation of said motor so as to cause said pump to deliver cleaning iiuid through said supply line when the difference in pressure exceeds a predetermined standard and to stop the motor so as to discontinue said supply when said standard is again attained, and timing mechanism for periodically operating said motor regardless of pressure conditions in the strainer.

4. The straining equipment of claim 1 wherein the cleaning iiuid supply line receives its supply from the outlet side of the straining equipment.

5. The straining equipment of claim 2 wherein the cleaning uid supply line receives its supply from the outlet side of the straining equipment.

6. The straining equipment of claim 3 wherein the cleaning iiuid supply line receives its supply from the outlet side of the straining equipment.

DANIEL R. MCNEAL. 

